This invention relates to a lamp-setting mechanism, particularly for photographic enlarging apparatus having a condenser-illuminating system.
For the copying of transparent, non-self-illuminating original copies, illuminating systems with condensers are employed in many apparatus, e.g. in photographic enlarging apparatus. In order to achieve an optimum illumination of the original copies at all copying scales, it is necessary to change the distance between the light source and the copying optics employed at a given time. This generally occurs by moving the light source relative to the condenser. Since the copying scale in enlarging apparatus is variable within wide limits, wherein additionally copying optics with varying focal lengths come into play, there results a relatively large adjusting range for the light source.
For the optimum illumination of the original copies, it is necessary, furthermore, that the filament and the bulb, respectively, of the light source be situated in a precisely determined position opposite the optical axis of the condenser.
A number of photographic enlarging apparatus provide for a follow-up and/or centering device for the light source within the illuminating system, so that their precise conformance to the particular optical conditions is made possible.
The known follow-up and centering devices, however, are suitable only for an occasional adjustment of the light source, because the respective controls are accessible only with difficulty and an adjustment is thus inconvenient. However, if point light sources are used in the illuminating system for the achievement of the greatest possible contrast, a change in the distance of the light source relative to the condenser is necessary in any change in the scale of enlargement, should optimum results be achieved.
A new centering of the light source is equally necessary with each new distance adjustment, because the respective guiding units within the illuminating system cannot be constructed because of cost reasons with the necessary great precision, and the optical axis of the condenser can be considered only within certain limits as precisely parallel to the course on which the light source is adjusted.
The object of the invention is to provide a lampsetting mechanism for a condenser illuminating system wherein the distance change and centering of the light source as compared to the condenser is related to the greatest possible comfort of operation.